1 files changed, 4 insertions, 2 deletions
diff --git a/synapse/config/sso.py b/synapse/config/sso.py
index 524a7ff3aa..11a9b76aa0 100644
--- a/synapse/config/sso.py
+++ b/synapse/config/sso.py
@@ -103,8 +103,10 @@ class SSOConfig(Config):
         # the client's.
         # public_baseurl is an optional setting, so we only add the fallback's URL to the
         # list if it's provided (because we can't figure out what that URL is otherwise).
-        if self.public_baseurl:
-            login_fallback_url = self.public_baseurl + "_matrix/static/client/login"
+        if self.root.server.public_baseurl:
+            login_fallback_url = (
+                self.root.server.public_baseurl + "_matrix/static/client/login"
+            )
             self.sso_client_whitelist.append(login_fallback_url)
 
     def generate_config_section(self, **kwargs):